Metallation of phenyl group induced by oxidation: carbene complexes of platinum(IV)

Abstract

The reactions of dichlorine with the complexes cis-[PtCl₂{C(NHR¹)(NHR²)}(PEt₃)], cis-[PtCl₂{C(OR³)(NHR²)}-(PR⁴₃)] and trans-[PtCl{C(NHR¹)(NHR²)}(PEt₃)₂][ClO₄](R¹²= Me or Et; R¹²= Me, Ph, 2,4-Cl₂C₆H₃, 2,6-Cl₂C₆H₃, 2-ClC₆H₄; R³= Me or Et; PR⁴₃= PEt₃ or PPh₃) have been examined. Where R¹= R²= Me, the platinum(IV)–carbene complexes [PtCl₄{C(NHMe)₂}(PEt₃)] and [PtCl₃{C(NHMe)₂}(PEt₃)₂][ClO₄] result, but where R¹= Me or Et and R²= Ph, 2-ClC₆H₄, or 4-ClC₆H₄; 2-metallation (and chlorine substitution in some cases) of the phenyl group occurs, giving the complexes [[graphic omitted]H₃Cl-4)}(PR⁴₃)], [[graphic omitted]H₃Cl-4)}(PEt₃)₂][ClO₄], and [[graphic omitted]H₃Cl-2)}(PEt₃)₂][ClO₄]. The i.r. and n.m.r. spectra of these complexes and possible reaction mechanisms are discussed. Treatment of trans-[PtBr{C(NHMe)₂}(PEt₃)₂][ClO₄] and trans-[PtBr{C(NHEt)(NHPh)}(PEt₃)₂][ClO₄] with dibromine gave trans-[PtBr₄(PEt₃)₂] as the only isolable product.